Where does the volt guage take its reading from?? (I know the battery) but specifically how does the wires run and where does it hook up to read the the voltage?

On my car when I turn the key to the on position before I start it it reads just above 8 volts and when I start it it reads between just above the 10 1/2 mark and 13. I checked the battery with a multi meter and with the car off it reads 12+ volts and with the car running it reads 14+ volts so I know the altinator is charging and the battery is fine.

What I am thinking is that the guage is some how miscalibrated or somewhere between the battery and the guage it is loosing some volts.

So if anyone knows how this curcuit is ran I would appreciate some help.

thanks
John